Hologram recording material, hologram recording method, and optical recording medium

Abstract

A hologram recording material is provided and has: a sensitizing dye absorbing light upon hologram exposure to generate an excited state thereof, and an interference fringes-recording component capable of causing color development reaction or discoloration by an electron or energy transfer (movement) form the excited state to record interference fringes providing a refractive index modulation. At least one of the sensitizing dye one the interference fringes-recording component is one a polymer and an oligomer.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a hologram recording material and hologram recording method which can be applied to high density optical recording medium, three-dimensional display, holographic optical element etc. BACKGROUND OF THE INVENTION [0002] The general principle of preparation of hologram is described in some literatures and technical books, e.g., Junpei Tsujiuchi, “Holographic Display”, Sangyo Tosho, Chapter 2. In accordance with these literatures and technical books, a recording object is irradiated with one of two fluxes of coherent laser beams and a photosensitive hologram recording material is disposed in a position such that all the lights reflected by the recording object can be received. Besides the light reflected by the recording object, the other coherent light is incident on the hologram recording material without hitting the object. The light reflected by the object is called object light. The light with which the recording materi...

AI Technical Summary

Benefits of technology

[0043] An object of an illustrative, non-limiting embodiment of the invention is to provide a hologram recording material and hologram recording method which can be applied to high density optical recording medium, three-dimensional display, holographic optical element, etc. and can attain a high sensitivity, high diffraction efficiency, good storage properties, low shrinkage factor, dry processing properties and multiplexed recording properties (high recording density) at the same time.

[0089] 3) a polymerization initiator which can initiate the polymerization of a polymerizable compound when electron or energy moves from the excited state of the sensitizing dye at the first step and from excited state of coloring material at the second step;

[0113] It was found that when the hologram recording material and method of the invention are used, hologram recording can be effected at a high diffraction efficiency, a small shrinkage, good dark storage properties and a linear rise of diffraction efficiency relative to exposure. Thus, the invention can be applied to holographic memory, etc. to advantage from the standpoint of capacity (recording density), system simplification by improvement of multiplexed recording properties, storage properties, etc.

Problems solved by technology

The amplified hologram is subject to drastic drop of light diffraction efficiency or reflectance due to absorption of light and thus is disadvantageous in percent utilization of light.

Under these circumstances, replaceable and random-accessible small-sized inexpensive optical recording media have been noted more than ever relative to magnetic tapes, which are not random-accessible, and hard discs, which are not replaceable and are subject to failure.

Thus, these two-dimensional recording media cannot be expected to have a recording capacity great enough to meet the future demand.

However, the hologram recording materials to be used in holographic memory have severer requirements than for the three-dimensional display and HOE as follows.

It is very difficult to meet these requirements at the same time.

However, none of these known volume phase type hologram recording materials cannot meet all these requirements particularly when used as high sensitivity optical recording medium.

In some detail, the gelatin bichromate process hologram recording material is advantageous in that it has a high diffraction efficiency and a low noise but is disadvantageous in that it has extremely poor storage properties, requires wet processing and exhibits a low sensitivity.

Thus, the gelatin bichromate process hologram recording material is not suitable for holographic memory.

The bleached silver halide process hologram recording material is advantageous in that it has a high sensitivity but is disadvantageous in that it requires wet processing and troublesome bleaching process, causes great scattering and has a poor light-resistance.

Thus, the bleached silver halide process hologram recording material, too, is not suitable for holographic memory.

The photorefractive hologram recording material is advantageous in that it is rewritable but is disadvantageous in that it requires the application of a high electric field during recording and has poor record storage properties.

The photochromic polymer process hologram recording material such as azobenzene polymer process hologram recording material is advantageous in that it is rewritable but is disadvantageous in that it has an extremely low sensitivity and poor record storage properties.

However, this type of a rewritable hologram recording material is disadvantageous in that since the quantum yield of isomerization of azobenzene is low and this process involves orientation change, the sensitivity is extremely low.

This type of a rewritable hologram recording material is also disadvantageous in that it has poor record storage properties, which are contrary to rewritability.

Thus, this type of a rewritable hologram recording material cannot be put into practical use.

However, the dry-processed photopolymer process hologram recording material is disadvantageous in that it has a sensitivity of about one thousandth of that of the bleached silver halide process hologram recording material, requires a heat-fixing step for about 2 hours to enhance diffraction efficiency, requires radical polymerization causing the effect of polymerization inhibition by oxygen and is subject to shrinkage after exposure and fixing and hence change of diffraction wavelength and angle during reproduction.

Further, the dry-processed photopolymer process hologram recording material is in the form of soft membrane and lacks storage properties.

It is thought that this disadvantage gives a great problem in transfer rate during practical use.

Further, the cationic polymerization process hologram recording material exhibits a reduced diffraction efficiency that probably gives a great problem in S / N ratio and multiplexed recording properties.

This causes a dilemma.

On the contrary, when the hologram recording material is arranged to have an enhanced sensitivity, the resulting storage properties and shrinkage resistance are deteriorated (radical polymerization process hologram recording material).

This gives a practically great problem.

The dilemma caused by the requirements for higher sensitivity, better storage properties and dry processing properties and the problem of multiplexed recording properties (high recording density) cannot be avoided from the physical standpoint of view so far as the related art photopolymer process hologram recording material is used.

It is also difficult for the silver halide process recording material in principle from the standpoint of dry processing properties to meet the requirements for holographic memory.

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